Extrusion die for two-ply seamless plastic tubing



Oct. 25, 1960 c. M. FIELDS ErAL EXTRUSION DIE.' FOR TWO-FLY SEAMLESSPLASTICVI'UBING 3 Sheets-Sheet 1 Filed July 12. 1957 IN VENTORS KATTORNEYS Ex'rRUsIoN DIE: FOR Two-FLY SEAMLESS PLASTIC TUBING Filed July12, 1957 Oct. 25, 1960 c. M. FIELDS Erm.

3 Sheets-Sheet 2 Oct. 25, 1960 c. M. FIELDS ETAL 2,957,201

EXTRUSION DIE FOR TWO-FLY SEAMLESS PLASTIC TUBING Filed July 12, 1957 3Sheets-Sheet 5 INVENTORS HZQ K. fczZZe and C72/arles M Fz'eiaf bij m, m@

ATTORNEYS United States Patent EXTRUSION DIE FOR TWO-PLY SEAMLESSPLASTIC TUBING Charles Marion Fields and Hugh Kenneth Mallett,Zanesville, Ohio, assignors to Continental Can Company, Inc., New York,N.Y., a corporation of New York Filed July 12, 1957, Ser. No. 671,477

3 Claims. (Cl. 18-13) ln the manufacture of seamless plastic tubing, itis quite common to force polyethylene or other thermoplastic materialthrough an extrusion die to shape the tubing. When so doing, however, ifvery thin walled tubing is being extruded, very minute pin holesfrequently occur in the tubing. It has therefore been proposed tosimultaneously extrude an outer tube and an inner tube in spacedconcentric relation and to bring the two tubes together beforeappreciable setting of the plastic. The two tubes thus become integrallyunited into a two-ply tube and there is Vlittle likelihood of any pinholes in either tube being in register with any similar holes in theother.

Die structures proposed for such dual extrusion have been rathercomplicated and expensive and diicult to adjust for orifice accuracy andfor producing tubing having dierent side wall thicknesses. The presentinvention, however, has aimed to provide a new and improved diestructure relatively free from such disadvantages.

A head, a ring and a separator are disposed in concentric relation, withsaid separator between said head and ring, said separator being spacedfrom said head and being cooperable therewith in forming an innercontinuous plastic extruding orice, said separator being also spacedfrom said ring and cooperating with the same in forming an outer plasticextruding orifice.

An object of the invention has been to provide an elongated mandrelcarrying the aforesaid head and disposed in a bore of the die body, thelower end of said mandrel being secured to said body and an intermediateportion of said mandrel being spaced from the wall of said bore toprovide a passage for conducting the plastic to the spaces between theaforesaid separator, head and ring.

Another object has been to provide for so securing the mandrel to thedie body that said mandrel may be easily adjusted longitudinally to varythe space between the mandrel head and the aforesaid separator, thuswidening or narrowing the -inner plastic extruding orifice according-Vto the thickness to zbe imparted to the inner extruded tubing.

'Still another object has been to provide a carrier adjustably mountedon the die body, to secure theaforesaid separator to said carrier formovement bodily therewith, and to adjustably mount the aforesaid ring onsaid carrier, the adjusting means for said carrier and ring permittingeasy radial adjustment of said separator yinto uniformly spaced relationwith the mandrel head, and correspondingly easy radial adjustment ofsaid ring into uniformly spaced relation with said separator.

Yet another object has been to provide a novel structure in which theaforesaid separator is formed with radial ports which place the spacebetween said separator and the mandrel head in communication with thespace between Said separator and the aforesaid ring, whereby the plasticfor both the inner and outer extruded tubes may be supplied through theabove mentioned passage between the mandrel and the wall of the bodybore.

A further object has been to provide the carrier with fice a lowerdownwardly projecting continuous flange surrounding the upper end of thedie body, to provide said carrier with an upper upwardly projectingcontinuous flange surrounding the lower portion of the aforesaid ring,to equip said lower flange with radial adjusting screws abutting saidbody for adjusting said carrier, to equip said upper flange with otherradial adjusting screws abutting said ring for adjusting this ring, toprovide clamping screws for securing said carrier to said body aftercarrier adjustment, and to provide other clamping screws for securingsaid ring to said carrier after ring adjustment, all of said clampingscrews having clearances permitting the required carrier and ringadjustments when these screws are slightly loosened.

A still further object is to provide a novel construction having maximumadvantages from both the standpoint of manufacture and use.

With the above and other objects in view that will hereinafter appear,the nature of the invention will be more clearly understood by referenceto the following detailed description, the appended claims and theseveral views illustrated in the accompanying drawings.

ln the drawings:

Figure 1 is a View partly in elevation but primarily in vertical sectionsubstantially on the lines 1-1 of Figures 2 and 3.

Figure 2 is a lower end View.

Figure 3 is a horizontal sectional view on line 3 3 of Figure 1.

Figure 4 is a perspective View of a plate embodied in the means foradjusting and securing the mandrel.

The preferred construction has been illustrated and will be specificallydescribed but attention is linvited to the possibility of makingvariations.

'Ihe die body 5 is provided with a lateral boss 6 for attachment to aconventional extruding machine. The upper end of this body 5 is formedwith an annular outwardly projecting flange 7, the upper side of saidflange and the upper end surface of said body being disposed in the samehorizontal plane. A cylindrical bore Sis formed vertically through thebody 5 and opens through both the upper and lower ends of said body,said bore being concentric with the flange 7. A bushing 9 is tightlysecured in the lower portion of the bore 8 and has its upper end surface10 disposed in an inclined plane, with the lowest portion of saidsurface 10 positioned toward the boss 6. A port 11 extends through thebody 5 and boss 6 and opens into the bore 8 `directly over the aforesaidlowest portion of the bushing end surface 10.

A cylindrical mandrel 12 extends longitudinally through the bore 8 andbushing 9 and contacts with the latter without appreciable clearance.The upper end of the mandrel 12 projects above the ange 7 and is shapedto form a conical head 13 having its apex disposed downwardly. The lowerend 14 of the mandrel 12 projects downwardly from the body 5 and isexternally threaded at 15. The intermediate portion of the mandrel 12 isspaced from the Wall of the bore 8 to provide a plastic conductingpassage 16 between said mandrel and said bore wall, said passage 16being in communication lwith the port 11. A longitudinal duct 17 isformed in the mandrel for a purpose to be later explained.

A horizontal plate 18 is located under the body 5 and is Secured to saidbody by screws 19, said plate 18 being provided on its upper side Withintegral lugs 20 which abut the lower end of said body 5 and space thebody portion of said plate downwardly from said lower end of said body5. This body portion of the plate 18 is formed with an opening 21through which the threaded lower end 14 of the mandrel 12 extendswithout contact. An upper nut 22 and a lower nut 23 are threaded ontothe mandrel end 15 and contact respectively with 3 the upper and thelower side of the plate 18. The mandrel 12 is Ythus rigidly securedtothe body 5, and by loosening either n ut and tightening the other,said man- Vdrel may bev vertically adjusted with precisionyfor a-purnected to this carrier 2.4 in communication with the port 47, V.anda preferably flexible tube 49 is connected with said valve. y

When the valve 48 is opened and ysub-atmospheric presvpose to be laterexplained. if y 5 sure is created in the tube 49, preferably by humanmouth A circular carrier 24V is disposed uponethe =upper Yend suction, acorresponding sub-atmospheric pressure is pro- 'of thebodypS Vand itsiiange 7, said carrierjhaving la-cenp duced in -the space 50 betweenVthe Vlower ends of the extral opening V25 registering with the upper'end of the i trudedV plastic tubes 32 and 38, to aid in bringing saidbody bore 8 to form with the mandrel y12 a ,continuation tubesintointegral union with eachother and to prevent of passage 16; Thecarrier 24 is secured tothe flange 7 10 appreciabletrapping of airbetween saidtubes.V However, by clamping screws 26, said screws havingclearance in as the ,tubesV are upwardlyrfed and united, it has been theange openings 27 to allow radial adjustments of the j Y found that aVsmall amount of `air from the space 50 is carrier 24 whenvsaid screwsare loosened: Vand radial adentrained with them, resulting in avery slowreduction justing screws 28 are provided for-making the Vadjustof thesub-atmospheric pressure in said space 50, and if ments. The carrier isformed witha downwardly prothe pressure dropfbe allowed tofbeoome toogreat, one or jecting continuous flange 29 through whichV the adjustingboth tubes will turn abruptly at the extruding orifice, conscrews 2S arethreaded withv `theinnner ends abutting tact with the end of the die andbreak off. Such an oc- `the edge of the flange 7, Vwhich edgeissurrounded by currence-is avoided by periodically Opening the valve 48 Ysaid flange 29. Y 'and restoring `the desired pressure.

By slightly loosening the clamping screws 26 and turn- 20 Y Air atabove-atmospheric pressure may be conducted ing the adjusting screws 28,the Vcarrier 24 maybe posifrom a blower or the like through the mandrelduct 17 Vtionally adjusted with precision. The carrier may then into theinner-tube 32, -to expandthe latter into integral Ybe locked in adjustedposition by re-tightening the clanipunion with theouter tube 38, and ifdesired such air presing screws 26.' Y Y sure may be suicient to expandboth tubes to impart a An upwardly ared separator 30 is secured upon the25 diameter to the finished tubing greater than the diameter carrier 24for adjustmenttbodily With'said carrier. This of the outer extrudingorifice 37. Expansion of both separator'3i) surrounds and is spaced fromthe mandrel tubes to a diameter greater than that/of the orifice 37 mayhead 13, and these two elements 30 and 13 coact in forinalso beeifected, if desired, by passing said tubes jointly ing an innercontinuous 0rifice.31 through .which to ex- Varound an internal coolingring but such a ring may be .trude an inner plastic tube 32. The space33 between 30 employed to merely expand the inner tube 32finto union theseparator 30 and the head 13 communicates with with the outer tube,Without appreciablyincreasing the the opening of the carrier 24. Thiscarrier has a diameter of the latter. countersink 34 in which the lowerend of the separator Contraction 0f both of the tubes 32 and 3S to adiamis secured by screws 35. AV ring 36 is secured upon eter less thanthat of the inner extrudingorifice 31, if v'the carrier24 and surroundsthe separator 30, said ring 35 desired, may be eifeeted by PaS-Sing bothtubes through and separator being spaced apart and coacting in formingall eXternal Cooling ring but Suell a ring may be uSed to anoutercontinuous orifice 37 through which to extrude merely contract theouter tube 38 into union with the invan'outer .plastic tube 38. The ring36 is secured upon YIleltube 32, Without aPPreeiably decreasing thediameter the carrier 24 by clamping screws 39 which have clearof thelatter. t V4ance in the carrier openings 40 to permit radial adjust- 40Coaeting niP rollS may be employed above the eXtruSion 'merits of thering upon the carrier. Radial adjusting die to upwardly Pull the tubingand to at least temporarily Vscrews 41 are provided for making theadjustments, these atten it after union of the inner and outer tubes andcool- VScrews 41 being threaded through an upwardly projecting ing. Suchattening prevents escape of pressure supplied continuous iiange 42 whichis formed on the carrier 24 through the mandrel duct 17. The completedtubing'may and. surrounds the lower portion of the ring 36, which 45 beWound on a reel in attened form or may be restored portion is abutted bythe inner ends of said screws 41. to circular cross sectional shapebeforeV reeling.

Y Byslightly loosening the clamping screws 39 and turn- To maintain theplastic at desired Vhigh temperature ing the adjusting screws 41 asrequired, the ring 36 may during its passage through the die, anysuitable die heating be positionally adjusted with precision. The ringmay means may be employed. Electric heaters are. diagramthen be lockedin adjusted position by re-tightening the matically illustrated at 51 inFigure l by broken lines. clamping screws 39. t From the foregoing, itwill be seen that a novel and The screws 26 and 28 are employed to -soadjust the advantageous construction has been disclosed forattainvcarrier 24 on the body 5 Vas to dispose the separator 30 'ing thedesired ends. However, attention is again invited in 'strictlyconcentric relation with the mandrel head 13, to the possibility ofmaking variations. Vthus insuring uniform radial width for the innerorice We claim: V31 through Wlileil the Inner PlaStle tube 32 iSeXtruded- 1. An extrusion die for two-ply seamless plastic tubing Thewidth of this orifice 31 and therefore the thickness.. comprising a bodyhaving a bore which opens through its of the tube wall, may be varied.as required by operating upper end, a mandrel disposed longitudinally insaid bore the nuts 22 and 23'to longitudinally adjust the mandrel andhaving a head above said body, the intermediate por- 12 andY ltS head 1-Thel SCreYVS 39 and 4l are em- 60 tion of said mandrel below said headbeing spaced from ployed to set the ring 36 in strictly concentric.relation the wall of said bore to provide a plastic conducting pasp wtihthe separator 30, thus insuring'uniform radial Width sage uniformlyspaced around said intermediate Yportion fo; thgesouter oriiice 37through which the outer plastic of said mandrel, lateral passage meansfor conducting a eube 11exti'u ed, resulting in uniform thickness ofplastic to said passage, means securing the lower end of v said mandrelto said body, a separator surrounding and The lower end portion of'theseparator 30 is formed outwardly uniformly spaced from said head, saidseparator withV a plurality of substantially radial ports 43 which. andhead coacting in forming an inner continuous plastic connect the Vspace33 between said separator and the Vextruding orifice, a ring surroundingsaid separator and 'mandrel head .13 with the space 44 betweensaidsepauniformly spaced therefrom, said ring and separator being Vratorandthe ring 36. The separator 30 also has a small 70 cooperable informing an outer continuous plastic extrudvertical port 45 from 'itsupper to its lower end; and said 'lower yend has a shallow groove 46with `which said port 45V communicates. This groove 46 communicates-with thejinner end of a small radial port 47 (Figure 3) f-Whichisfoi=med in the carrier' 24. A valve 48 is coning orifice, andcentering means mounting said Separator andV said ring on said body withVthe aforesaid passage in communication with the space between saidseparator and said head, said separator having radial passages extending'from the lowelrnost portions of said space to the lowermost portion ofthe space between said separator and said ring at the uppermost portionof said passage, said mounting means for said separator and said ringincluding a carrier to which said separator and said ring are secured,and second centering means securing said carrier to said body, saidmeans securing the lower end of said mandrel to said body includingadjusting means for longitudinally adjusting said mandrel, said head andSaid separator having coaeting surfaces effective to vary the size ofsaid inner orifice when said mandrel is longitudinally adjusted.

2. An extrusion die for two-ply seamless tubing comprising a body having`a bore which opens through its upper end, a mandrel disposedlongitudinally in and projecting upwardly from said bore, the upper endof said mandrel being provided with a head, the intermediate portion ofsaid mandrel below said head being uniformly spaced from the wall ofsaid bore to provide a plastic conducting passage around saidintermediate portion of said mandrel, lateral passage means forconducting a plastic to said passage, means securing the lower end ofsaid mandrel to said body, a carrier resting upon -the upper end of saidbody and having an opening registering with the upper end of said boreand forming a continuation of said passage, said carrier having adownwardly projecting ange surrounding and spaced from said upper end ofsaid body, clamping screws securing said carrier to said body, saidclamping screws having clearance permitting radial adjustments of saidcarrier with respect to said mandrel, radial adjusting screws threadedthrough said flange and abutting said body for eecting said radialadjustments of said carrier, a separator projecting upwardly from saidcarrier and secured thereto for radial adjustment bodily with saidcarrier, said separator surrounding and being unifomly spaced from saidhead, the space between said separator and said head being incommunication with said opening of said carrier the upper ends of saidseparator and head being cooperable in forming an inner continuousplastic extruding oriiice, a ring resting upon said carrier, said ringsurrounding said separator and being spaced therefrom, additionalclamping screws securing said ring upon said carrier and havingclearance permitting radial adjustments of said ring with respect tosaid separator, and additional radial adjusting screws for effectingsaid radial adjustments of said ring, said carrier having a continuousupwardly projecting flange surrounding and uniformly spaced from thelower portion of said ring, said additional radial adjusting screwsbeing threaded through this flange, said separator having radialopenings from the lowermost portion of the space between said separatorand said head to the lowermost portion of the space between saidseparator and said ring at the uppermost portion of said passage, theupper end of said separator being cooperable with said ring in formingan outer continuous plastic extruding orice.

3. A structure as speciiied in claim 2, in which said means securing thelower end of said mandrel to said body includes adjusting means forlongitudinally adjusting said mandrel, said head and said separatorhaving coacting surfaces eiective to vary the size of said inner oriticewhen said mandrel is longitudinally adjusted.

References Cited in the le of this patent UNlTED STATES PATENTS2,057,467 Williams Oct. 13, 1936 2,633,602 Sverdrup Apr. 7, 19522,753,596 Bailey July 10, 1956 2,760,230 Van Riper Aug. 28, 19562,859,476 Lainson Nov. 11, 1958

